1. Field of the Invention
The present invention relates to a method of and apparatus for upgrading heavy hydrocarbon feeds. In particular, the method and apparatus include gasification of heavy high-carbon content by-products produced by the upgrading of the heavy hydrocarbon feeds.
2. Description of the Prior Art
Many types of heavy crude oils contain high concentrations of sulfur compounds, organo-metallic compounds and heavy, non-distillable fractions called asphaltenes which are insoluble in light paraffins such as normal pentane. Because most petroleum products used for fuel must have a low sulfur content to comply with environmental regulations and restrictions, the presence of sulfur compounds in the non-distillable fractions reduces their value to petroleum refiners and increases their cost to users of such fractions as fuel or raw material for producing other products. It is desirable to remove the non-distillable fractions, or asphaltenes, from the oil because not only do the non-distillable fractions contain high amounts of sulfur, the asphaltenes tend to solidify and foul subsequent processing equipment. Removal of the asphaltenes also tends to reduce the viscosity of the oil.
Solvent extraction of asphaltenes is used to process crude and produces deasphalted oil (DAO) which is subsequently further processed into more desirable products. The deasphalting process typically involves contacting a heavy oil with a solvent. The solvent is typically an alkane such as propane, butane and pentane. The solubility of the solvent in the heavy oil decreases as the temperature increases. A temperature is selected wherein substantially all the paraffinic hydrocarbons go into solution, but where a portion of the resins and asphaltenes precipitate. Because the solubility of the asphaltenes is low in the oil-solvent mixture, the asphaltenes will precipitate out and are further separated from the DAO.
In order to increase the saleability of these hydrocarbons, refiners must resort to various expedients for removing sulfur compounds. A conventional approach for removing sulfur compounds in distillable fractions of crude oil is catalytic hydrogenation in the presence of molecular hydrogen at moderate temperature and pressure. While this approach is cost effective in removing sulfur from distillable oils, problems arise when the feed includes metal-containing asphaltenes. Specifically, the presence of the metal-containing asphaltenes results in catalyst deactivation by reason of the coking tendency of the asphaltenes, and the accumulation of metals on the catalyst.
Many proposals thus have been made for dealing with non-distillable fractions of crude oil and other heavy hydrocarbons, include residual oil which contain sulfur and other metals. And while many are technically viable, they appear to have achieved little or no commercialization due in large part to the high cost of the technology involved. Usually such cost takes the form of increased catalyst contamination by the metals and/or carbon deposition resulting from the attempted conversion of the asphaltene fractions.
One way that refineries have attempted to receive more value from heavy hydrocarbons including asphaltenes has been to gasify them. U.S. Pat. No. 4,938,862 to Visser et al. discloses a process for thermal cracking residual hydrocarbon oils involving feeding the oil and a synthetic gas to a thermal cracker, separating the cracked products into various streams including a cracked residue stream, separating the cracked residue stream into an asphaltene-rich stream and an asphaltene-poor stream, then gasifying the asphaltene rich stream to produce syngas which is fed to the thermal cracker.
Likewise, U.S. Pat. No. 6,241,874 to Wallace et al. discloses extracting asphaltenes through with a solvent and gasifying the asphaltenes in the presence of oxygen. Heat from the gasification of the asphaltenes is used to help recover some of the solvent used in extracting the asphaltenes.
Further, U.S. Pat. No. 5,958,365 to Liu discloses processing heavy crude oil by distilling the same, solvent deasphalting the oil, and further processing the heavy hydrocarbons to produce hydrogen. The hydrogen is used to treat the deasphalted oil fraction and distillate hydrocarbon fractions obtained from the heavy crude oil.
However, there still remains a need for a cost-effective and commercially viable method of extracting more value out of asphaltenes produced in refineries.
Applicants have unexpectedly developed an apparatus for producing sweet synthetic crude from a heavy hydrocarbon feed comprising:
a) an upgrader for receiving said heavy hydrocarbon feed and producing a distillate fraction including sour products, and high-carbon content by-products;
b) a gasifier for receiving said high-carbon content by-products and producing synthetic fuel gas and sour by-products;
c) a hydroprocessing unit for receiving said sour by-products and hydrogen gas, thereby producing gas and said sweet crude; and
d) a hydrogen recovery unit for receiving said synthetic fuel gas and producing further hydrogen gas and hydrogen-depleted synthetic fuel gas, said further hydrogen gas being supplied to said hydroprocessing unit.
Applicants have further developed a method for producing sweet synthetic crude from a heavy hydrocarbon feed comprising:
a) upgrading said heavy hydrocarbon feed in an upgrader and thereby producing a distillate feed including sour products, and high-carbon content by-products;
b) gasifying in a gasifier said high-carbon content by-products and producing synthetic fuel gas and sour by-products;
c) hydroprocessing said sour products along with hydrogen gas, thereby producing gas and said sweet crude; and
d) recovering hydrogen in a hydrogen recovery unit from said synthetic fuel gas and producing further hydrogen gas and hydrogen-depleted synthetic fuel gas, and supplying said further hydrogen gas to said hydroprocessing unit.
Furthermore, Applicants have unexpectedly developed an apparatus for producing sweet synthetic crude from a heavy hydrocarbon feed comprising:
a) an upgrader comprising:
I. a distillation column for receiving said heavy hydrocarbon feed and producing a distillate fraction, and a non-distilled fraction containing sulfur, asphaltene and metals;
II a solvent deasphalting unit for processing said non-distilled fraction and producing a deasphalted oil stream and an asphaltene stream, an outlet of said deasphalting unit containing said deasphalted oil being connected to an inlet of a thermal cracker and wherein said asphaltene stream comprises said high-carbon by-products;
III said thermal cracker thermally cracking said deasphalted oil and forming a thermally cracked stream;
b) a gasifier for gasifying said asphaltenes in the presence of air or oxygen and producing ash and a gas mixture:
c) a scrubber which receives said gas mixture and water and produces sour water and a clean sour gas mixture;
d) a first gas processor which receives said clean sour gas mixture and produces a sweet synthetic fuel gas, said first gas processor comprises:
I a solvent contactor which receives lean solvent from a solvent regenerator and said clean sour gas mixture and produces a sweet product and rich solvent;
II said solvent regenerator receiving said rich solvent and producing said lean solvent and acid gas;
III a sulfur recovery unit which receives said acid gas and produces sulfur and a sulfur-depleted gas which is vented to the atmosphere; and
IV a liquid recovery unit which receives said sweet product and produces sweet gas, sour water and light liquid hydrocarbons;
e) a hydroprocessing unit for receiving said sour products and hydrogen gas, thereby producing gas and said sweet crude, said hydroprocessing unit comprising:
I a hydroprocessor which receives said distillate feed and hydrogen gas and produces a high-pressure hydroprocessed product;
II a first flash vessel which receives said high-pressure hydroprocessed product and produces high pressure sour gas and high pressure flashed product;
III a second flash vessel which receives said high pressure flashed product and produces low pressure sour gas and low pressure flashed product;
IV a stripper which receives said low pressure flashed product and steam and produces low pressure sour gas, sour water and sweet synthetic crude;
V a first solvent contactor in fluid communication with a first solvent regenerator and containing a clean solvent, said first solvent contactor receiving said high pressure high pressure sour gas from said first flash vessel and producing sweet recycle gas which is fed to said hydroprocessor and sour solvent, said first solvent regenerator receiving said sour solvent and producing said clean solvent which is fed to said first solvent contactor and hydrogen sulfide and ammonia; and
VI a second solvent contactor in fluid communication with a second solvent regenerator and containing clean solvent, said second solvent contactor receiving said low pressure sour gas from said second flash vessel and from said stripper and producing fuel gas and sour solvent, said second solvent regenerator receiving said sour solvent and producing said clean solvent which is fed to said second solvent contactor.; and
f) a hydrogen recovery unit for receiving said synthetic fuel gas and producing further hydrogen gas and hydrogen-depleted synthetic fuel gas, said further hydrogen gas being supplied to said hydroprocessing unit.